/Engine/Source/Developer/DerivedDataCache/Public/DerivedDataCacheInterface.h
Synchronously checks the cache and if the item is present, it returns the cached results, otherwise tells the deriver to build the data and then updates the cache
true if the data was retrieved from the cache or the deriver built the data sucessfully. false can only occur if the plugin returns false.
bool GetSynchronous ( class [FDerivedDataPluginInterface](API\Developer\DerivedDataCache\FDerivedDataPluginInterface) * DataDeriver, [TArray](API\Runtime\Core\Containers\TArray)< uint8 > & OutData, bool * bDataWasBuilt )